This is a proposal to take advantage of ongoing research on family formation int he Nepalese Himalayas to investigate the reciprocal relations between changes in population processes (family formation and migration) and the environment (land use, soil quality, water quality, and flora). The aim of the project proposed here is to gather additional data on environmental quality and population processes and link it to data on neighborhood contexts and family formation from the Chitwan Vally Family Study (currently being funded by NICHD), for the purpose of analyzing reciprocal links between population processes and environmental changes. The data will be used to address three specific questions regarding the reciprocal relations between population processes and the environment; 1) To what extent do changes in marriage timing, household fission, childbearing, and migration influence changes in land use, soil quality, water quality, and flora diversity? 2) To what extent do variaitons in land use, soil quality, water quality, and flora diversity, produce changes in marriage, household fission, childbearing, and migration? and 3) To what extent are the observed relationships between population processes and the environment produced by exogenous changes in the social and institutional context? Existing historical data on environmental factors will be merged with historical data on community-level social and institutional changes, and individual-level histories of demographic events being gathered by the Chitwan Valley Family Study (CVFS). We will also collect new measures of variation in environmental factors in the 150 neighborhoods being studied by the CVFS for two time periods, and maintain a 3-year household registry from the 1650 sampled households between these time periods, including monthly updates on major demographic events and seasonal updates on agricultural activities. By taking detailed measures of environmental variations at two points in time and maintaining a systematic registry of agricultural organization and population events during the intervening time, these data will provide the means to asses the reciprocal relations between population processes and changes in environmental quality over time. Finally, by linking these new data together with data (from the CVFS) on the hanging social and institutional contexts in these communities, we will be able to explore the extent to which these contextual changes produce athe observed links between population and the environment. These dat will be linked together using a geographic information system, or GIS. The GIS format will allow us to link spatial variaitons in environmental factors to specific households and individuals, and will also be used to link our data on spatial variations in community contexts to the populations and environment data. Analyses will feature use of event history techniques to estimate our models. These techniques allow us to use the temporal order of events to estimate the reciprocal relationships between population and environmental changes.